On Fri, Mar 18, 2022 at 05:03:34PM +0600, NRK wrote:
> the array is not accessed outside of base64dec() so it makes sense to
> limit it's scope to the related function. the static-storage duration of
> the array is kept intact.
>
> this also removes unnecessary explicit zeroing from the start and end of
> the array. anything that wasn't explicitly zero-ed will now be
> implicitly zero-ed instead.
>
> the validity of the new array can be easily confirmed via running this
> trivial loop:
>
> for (int i = 0; i < 255; ++i)
> assert(base64_digits[i] == base64_digits_old[i]);
>
> lastly, as pointed out by Roberto, the array needs to have 256 elements
> in order to able access it as any unsigned char as an index; the
> previous array had 255.
>
> however, this array will only be accessed at indexes which are
> isprint() || '=' (see `base64dec_getc()`), so reducing the size of the
> array to the highest printable ascii char (127 AFAIK) + 1 might also be
> a valid strategy.
> ---
> st.c | 22 +++++++---------------
> 1 file changed, 7 insertions(+), 15 deletions(-)
>
> diff --git a/st.c b/st.c
> index 1307fdf..f43cfd3 100644
> --- a/st.c
> +++ b/st.c
> @@ -349,21 +349,6 @@ utf8validate(Rune *u, size_t i)
> return i;
> }
>
> -static const char base64_digits[] = {
> - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 62, 0, 0, 0,
> - 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, -1, 0, 0, 0, 0, 1,
> - 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
> - 22, 23, 24, 25, 0, 0, 0, 0, 0, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34,
> - 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 0,
> - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> - 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
> -};
> -
> char
> base64dec_getc(const char **src)
> {
> @@ -377,6 +362,13 @@ base64dec(const char *src)
> {
> size_t in_len = strlen(src);
> char *result, *dst;
> + static const char base64_digits[256] = {
> + [43] = 62, 0, 0, 0, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
> + 0, 0, 0, -1, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
> + 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0,
> + 0, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
> + 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
> + };
>
> if (in_len % 4)
> in_len += 4 - (in_len % 4);
> --
> 2.34.1
>
>
Thank you for both patches,
I like how this discussion and testing was going and found these 2 bugs.
Applied both patches,
--
Kind regards,
Hiltjo
